1. Field of the Invention
This invention relates to the field of wireless data transfer and communication. In particular it relates to the wireless transfer of data at high speed using infra-red radiation.
2. Description of the Related Art
Many business and personal applications require the high speed wireless transfer of data between core and peripheral electronics equipment. In many instances, particularly when the data transfer occurs within a limited spatial region, the use of infra-red radiation is a method of choice. Examples of personal data transfer applications utilizing infra-red radiation include remote controllers for home appliances, home safety and security systems, communication between personal computers and peripherals and wireless headphones. Silver (U.S. Pat. No. 4,882,745) provides a cordless headset telephone that allows for xe2x80x9chands-freexe2x80x9d operation and is connected to a base unit by either radio-frequency or infra-red radiation. Ito (U.S. Pat. No. 5,708,725) provides an easily adjustable wireless headphone that can be used to receive audio signals transmitted by infra-red radiation. Examples of business applications include local area networking between computers and peripheral devices. Kerklaan, et al. (U.S. Pat. No. 5,861,968) provides an infra-red transceiver for use with a computer in a wireless local area network (LAN). In all of these applications, the use of infra-red radiation as the medium of data transfer provides advantages such as economy of operation and the fact that there is no need to comply with the various regulations that govern wireless data transfer by other forms of electromagnetic radiation such as microwave or radio frequency transmissions.
There are, however, some disadvantages associated with wireless infra-red transmissions. Because the transmitting unit of the wireless infra-red radiation is generally a low power source that is not highly directional, the receiving unit must be capable of detecting low energy signals and have a reasonably isotropic reception area. This is particularly true if the receiver or transmitter are in motion relative to each other or at positions that can vary during use. In addition, infra-red transmitting devices are often used in areas where there is both ambient visible light and radio frequency energy, both of which can interfere with the reception of the infra-red radiation. Finally, the sensitivity of the photodetectors (photo-diodes) typically used to detect infra-red radiation is subject to variations with temperature changes, making a stable temperature environment highly desireable.
If the infra-red transmission is required to be point-to-point (i.e., propagate accurately between fixed locations), the use of optical fibers, light transmitting tubes or systems of directional reflectors may be necessary. Koyama (U.S. Pat. No. 5,953,145) provides accuracy and reliability by the use of a dual-mode transmission system that combines wireless infra-red signals with signals transmitted along an optical fiber. Allen (U.S. Pat. No. 4,977,618) provides point-to-point wireless transmission by the use of a system of reflecting surfaces. Moseley et al. (U.S. Pat. No. 5,987,205) provides a flexible, hollow plastic tube to transmit infra-red energy between a transmitter and receiver disposed adjacent to each other. The wireless transceiver provided by Kerklaan and cited above includes a multi-beam deflector to maximize dispersion of an array of infra-red beams and provides a revolving turret for directional capabilities. Finally, the need to concentrate infra-red radiation for reliable detection extends even to the fabrication of integrated solid-state radiation detectors. Radford et al. (U.S. Pat. No. 5,721,429) provides an array of infra-red radiation sensitive Group II-VI alloy semiconductor material in a fabricated structure that utilizes internal reflections from mesa sidewalls and other reflective material to achieve a concentration of the infra-red radiation onto a smaller area.
Although Silver and Ito, cited above, use infra-red wireless communication between headsets and surrounding equipment, they provide no specific design for an infra-red receiving unit that will be sensitive, interference free and not subject to temperature fluctuations in photo-diode properties. Kerklaan et al., cited above, provides for the dispersion of a plurality of infra-red radiation beams, but does not make specific provision for detection of said beams in a manner that is sensitive, free of interference and not subject to temperature fluctuations. Allen, cited above, provides for a fixed array of reflectors and a transmitter and receiver at similarly fixed locations. Said method of data transfer is not applicable when the transmitter and receiver are in relative motion or have varying positions. Similarly, Koyama, cited above, does not provide what is strictly a wireless connection and freedom and degree of motion is limited by the use of an optical fiber. In a similar manner, Moseley et al., cited above, requires a relatively fixed relationship between the transmitter and receiver. The present invention specifically addresses the problems of receiver mobility, infra-red energy concentration, optical and radio frequency interference and temperature sensitivity that characterize infra-red receiver designs of the prior art.
A first object of this invention is to provide a receiver of wireless infra-red radiation that is suitable for use in high speed data transmission.
A second object of this invention is to provide a receiver of wireless infra-red radiation that will concentrate incident infra-red energy and render it of sufficient intensity to allow accurate decoding of data signals.
A third object of this invention is to provide a receiver of wireless infra-red radiation that is shielded from the effects of radio-frequency (RF) interference and prevent build-up of static electrical charges that may affect the photo-diodes"" pre-amplifier performance.
A fourth object of this invention is to provide a receiver of wireless infra-red radiation that reduces the effects of interference from ambient visible light.
A fifth object of this invention is to provide a receiver of wireless infra-red radiation that reduces the effects of temperature fluctuations.
A sixth object of this invention is to provide a receiver of wireless infra-red radiation that permits movement between it and the source of said radiation.
A seventh object of this invention is to provide a receiver of wireless infra-red radiation satisfying all of the above objects yet is of simple construction and small enough to fit on a personal headset or to be used in any of the many applications involving the wireless transmission of data at high speeds.
The objects of the present invention will be achieved by a semi-spherical front-end receiver design that utilizes a small array of photo-diodes, each mounted at the approximate focus of a concave reflecting surface, with the whole system surrounded by a grounded, conducting wire mesh and a cover that is transparent to infra-red frequencies.